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IEEE International Conference on Electronic Measurement & Instruments

Sinusoidal Noise Suppression in SERF Co-magnetometers with Allan Variance Validation

Z X Liu, Yifan Yan, Lele Ma, Haoying Pang, Zhuo Wang, Jixi Lu

Published Aug 22, 2025• 0 citations
Publisher

Abstract

Spin-exchange relaxation-free (SERF) co-magnetometers, characterized by high sensitivity, compactness, and low drift, show great potential in quantum precision measurements based on atomic ensembles. However, periodic fluctuation noise—originating from laser intensity instability, heating signal crosstalk, and electronic interference—induces oscillatory artifacts in Allan variance analysis, degrading measurement accuracy and long-term stability. This study presents a periodic noise suppression scheme based on jointly optimized finite impulse response (FIR) notch filters, implemented for the first time in a SERF co-magnetometer. By precisely shaping the amplitude response through least-squares optimization, the scheme achieves targeted attenuation of interference frequencies. Experimental results confirm that the proposed method effectively suppresses periodic noise, yielding smoother Allan variance curves and significantly enhancing measurement stability. The proposed approach offers a practical and generalizable solution for improving the precision of atomic sensors and provides technical guidance for noise mitigation in broader precision measurement applications.

DOI
10.1109/icemi66537.2025.11306403

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The long-term bias stability of spin-exchange relaxation-free atomic co-magnetometers is significantly constrained by coupled opto-thermal fluctuations. Traditionally, random systemic offsets at the magnetic compensation point lead to inconsistent opto-thermal coupling, compromising the reproducibility of sensor performance. In this work, we propose a method to simultaneously decouple and suppress these primary drifts by precisely characterizing the physical null-point of the atomic ensemble. A combined compensation scheme, joining residual rotation angle alignment and transverse magnetic field adjustment, is implemented to isolate the sensor output from fluctuations in probe laser intensity and vapor cell temperature. Experimental results demonstrate that the sensitivities to temperature drifts and probe power fluctuations are suppressed simultaneously at the identified null-point by factors of 72 and 880, respectively. This approach establishes a stable zero point, which is expected to significantly enhance sensor reproducibility and stability without sacrificing fundamental sensing performance.
The ultra-sensitive atomic co-magnetometer based on the spin-exchange relaxation-free (SERF) regime is a valuable tool for inertial measurements and fundamental physics research. However, the optical magnetic misalignment effect is a significant source of error in SERF co-magnetometers, limiting their magnetic field suppression ability and long-term stability. This paper establishes a response model of angular velocity and magnetic field for the SERF co-magnetometer. The impact of optical magnetic misalignment on the scale factor, magnetic field amplitude-frequency response, and angular velocity errors caused by magnetic noise is systematically investigated. The results indicate that the scale factor and magnetic field suppression ability decrease as the optical magnetic misalignment angle increases, while the angular velocity errors caused by magnetic noise increase as the misalignment angle increases. Finally, experimental results demonstrate that the optical-magnetic misalignment effect significantly compromises the long-term stability of SERF co-magnetometers, underscoring its substantial influence on the overall performance. This work contributes to understanding the mechanism of optical magnetic misalignment effects on the SERF co-magnetometer and enhances its performance.
Abstract Stochastic magnetic field noise has a non‐negligible negative impact on the performance of quantum precision measurement instruments such as spin‐exchange relaxation‐free (SERF) co‐magnetometer in terms of sensitivity and stability. Conventional magnetic field error analysis and suppression methods are not applicable to stochastic magnetic field noise. In this paper, a stochastic model of the SERF co‐magnetometer is proposed to analyze the mechanism of stochastic magnetic field noise. The mean and covariance propagation model of the SERF co‐magnetometer is given based on the stochasticity model and statistical principles. The analysis of simulation experiments reveals that reducing the longitudinal electron spin polarization can somewhat reduce the standard deviation of the system output caused by stochastic magnetic field noise. And the atomic ensembles are most resistant to stochastic magnetic field noise when the electron spin polarization strongly couples with the nuclear spin polarization. Finally, the experiments verified the above conclusions. In conclusion, this paper provides theoretical and experimental support for analyzing and suppressing the effect of stochastic magnetic field noise on the SERF co‐magnetometer, which is of great significance for improving the sensitivity and stability of the measurement.
Quantum manipulation technology and photoelectric detection technology have jointly facilitated the rapid development of ultra-sensitive atomic spin magnetometers. To improve the output signal and sensitivity of the spin-exchange-relaxation-free (SERF) atomic spin magnetometer, the noises influencing on the output signal and the sensitivity were analyzed, and the corresponding noise suppression methods were presented. The magnetic field noises, including the residual magnetic field noise and the light shift noise, were reduced to approximately zero by employing the magnetic field compensation method and by adjusting the frequency of the pump beam, respectively. With respect to the operation temperature, the simulation results showed that the temperature of the potassium atomic spin magnetometer realizing the spin-exchange relaxation-free regime was 180 °C. Moreover, the fluctuation noises of the frequency and the power were suppressed by using the frequency and the power stable systems. The experimental power stability results showed that the light intensity stability was enhanced 10%. Contrast experiments on the sensitivity were carried out to demonstrate the validity of the suppression methods. Finally, a sensitivity of 13 fT/Hz(1/2) was successfully achieved by suppressing noises and optimizing parameters.
The atomic comagnetometers (ACMs) based on the spin-exchange relaxation-free (SERF) regime exhibit extremely high sensitivity in angular velocity measurements, positioning them as leading candidates for next-generation precision inertial sensing. However, magnetic noise remains a significant factor that contributes significantly to long-term bias drift. Here, a comprehensive model in full-frequency band of the angular velocity measurement error induced by magnetic noise in ACMs is established. Based on the proposed model, what we believe to be a new method is proposed to reduce magnetic noise error by suppressing the magnetic field response in the mid-frequency range. After optimizing the temperature of the vapor cell to minimize the magnetic field response in the mid-frequency range, the angular velocity measurement error caused by magnetic noise was reduced by 20.4%, and the bias drift was improved by 34.8%. The theories and methods proposed in this study innovatively highlight the critical role of mid-frequency magnetic field responses in suppressing magnetic noise errors, and provide important guidance for improving bias drift in SERF ACMs.